1. Field of the Invention
This invention relates to an embroidery data producing device and embroidery data producing program, and more particularly to such an embroidery data producing device and program capable of producing data of offset line formed by moving an outline defining an embroidery area inside the embroidery area.
2. Description of the Related Art
It is generally known that underlying stitches are sewn under embroidery stitches with a lower thread density than the embroidery stitches when a part of work cloth inside an outline is filled with the embroidery stitches so that an embroidery pattern is sewn. The underlying stitches sewing is carried out in order to provide a three-dimensional effect on the lock stitches sewn over them or in order to prevent the work cloth from shrinking during the lock stitch sewing, thereby improving sewing quality.
Data of the aforesaid underlying stitch sewing is generally produced by an embroidery data producing device. The embroidery data producing device produces data of offset line obtained by moving an outline defining an embroidery area inside by a predetermined offset width (1 mm, for example). A plurality of needle points for underlying stitch are formed on the produced offset line. The needle points for underlying stitch are sequentially connected zigzag to one another so that underlying stitch sewing data is produced. An embroidering and sewing machine carries out an underlying stitch sewing based on the produced underlying stitch sewing data.
On the other hand, when embroidering and sewing is to be executed in a set sewing order, an inside running stitch sewing is sometimes carried out in order that a needle location may be moved to a predetermined sewing start location. The inside running stitches are sewn over the offset line formed near the outline so as to be inconspicuous even when the thread density for embroidery stitch is low.
Furthermore, when an appliqué cloth piece is sewn onto work cloth in appliqué sewing, data of offset line inside an outline of the appliqué cloth piece is produced. The appliqué cloth piece is sewn onto work cloth on the basis of the produced data.
The above-described offset lines are produced so as to be moved by the offset width inward from the outline defining the embroidery area. Accordingly, when two opposed outlines include respective portions coming close to each other, a part of a continuous offset line intersects another part of the offset line (referred to as “self-intersection”) or an offset line and outline intersect each other (referred to as mutual intersection”). Improving the sewing quality is difficult when underlying stitch sewing, inside running stitch sewing or other stitch sewing related to appliqué is carried out on the basis of the aforesaid offset line data.
U.S. Pat. No. 5,823,127 assigned to the same assignee as the present application discloses an embroidery data processing apparatus which is provided for an embroidery machine and is capable of producing underlying stitch data even when an offset line self-intersects. The disclosed embroidery data processing apparatus divides an underlying stitch area into a plurality of partial underlying stitch sewing areas encompassed by the offset line with the self-intersection point serving as a boundary point when the produced offset line has self-intersected. Furthermore, regarding each partial underlying stitch sewing area, whether an offset point is located inside the outline is determined. Data of auxiliary underlying stitch sewing is produced for the partial underlying stitch sewing area in which even at least one offset point is located outside the outline. On the other hand, partial underlying stitch sewing data is produced in a usual manner regarding each partial underlying stitch sewing area in which all the offset points are located inside the outline.
When the auxiliary underlying stitch sewing data is produced, the embroidery data processing apparatus extends a straight line obtained by connecting an offset point located between two self-intersection points and an apex of the outline. The apparatus then obtains a point of intersection at which the straight line and the outline intersect each other. The apparatus further obtains a middle point between the point of intersection and the apex of the outline and sequentially connects the self-intersection point and all the middle points, thereby producing data of running stitch sewing. The produced running stitch sewing data is used as auxiliary underlying stitch sewing data.
However, the above-described embroidery data processing apparatus does not dissolve the self intersection itself. Accordingly, the control of calculation for production of embroidery data is rendered complicated since a plurality of partial underlying stitch sewing data need to be produced for the underlying stitch sewing area. Particularly when the auxiliary underlying stitch sewing data is produced for the area between the self intersection points, the embroidery data processing apparatus is required to calculate the straight line between the offset point and the apex, the intersection point between the straight line and the outline, and the middle point between the intersection point and the apex. Thus, complicated calculation control is required. Furthermore, the calculation control is also complicated when the aforesaid technique is applied to production of an offset line for inside running stitch sewing and appliqué stitch sewing.
Furthermore, the aforesaid auxiliary underlying stitch sewing is substantially straight running stitch sewing. Accordingly, when the auxiliary underlying stitch sewing is used as the underlying stitch sewing, proper effects of underlying stitch sewing cannot sometimes be achieved sufficiently in the respects of the strength in the area of work cloth to which the auxiliary underlying stitch sewing has been applied, the shrinkage in the work cloth during embroidery stitch sewing, the three-dimensional effect of the embroidery pattern in the embroidery area and the like.
Yet furthermore, the foregoing technique is difficult to apply to production of data for appliqué stitch sewing in the case where an appliqué cloth piece is sewn along an offset line offset inside an outline of the appliqué cloth piece by a predetermined width. The reason for this is that two portions sewn by the appliqué stitch sewing are overlapped in the narrow area when the appliqué stitch sewing is carried out using auxiliary underlying stitch sewing data in a narrow area of the appliqué cloth piece.